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 GSM/SMS REMOTE TERMINAL UNIT

The ST23 Remote Terminal Unit (RTU) is a Malaysia made micro-controller based intelligent and versatile measurement and control unit. The system is robust in design and compactly constructed to suit applications in harsh industrial environments.

The RTU is designed to be placed at remote hydrological station to monitor river water level and/or rainfall. The acquired measurement will be transferred in form of Short Messaging System (SMS) back to the Central Monitoring System (CMS) through GSM Mobile Network. The field measurement or status data is monitored by the RTU by it’s digital inputs or analog inputs. The digital inputs include door open security alarm, float-switches cut-in/ cut-off levels or any other status obtained from transducers and switches. The RTU is capable of receive 4-channels of analog input in form of 4-20mA industrial standard current loop. Hence, the RTU can measure 4 analog measurement concurrently, such as water level, water quality such as turbidity, de-solve oxygen, chlorine, etc.

     Features
 
The ST23 RTU is designed for reliability and low power operation. It is equipped with most of common feature required for remote data monitoring as well as data logging. The following is the summary of it’s features:
 

  • Single Board Design for easy Operation & Maintenance

  • Industrial Grade 68HC11 based mico-controller for reliable operation

  • User friendly user interface through 4x4 matrix keypad and 2rows x 20 column Liquid Crystal Display (LCD) interface.

  • Large non-volatile RAM memory (128 Kbyte) as ring type buffer for data logging, able to Time-Stamp and Log Data internally up to a period of minimum 4 months when 15 minutes data logging is utilized. The non-volatile memory able to store data for minimum 10 years without external power

  • Upgradable software flexibility using removable EPROM. Program memory never corrupted due to internal interruption

  • Year 2000 compliant Real-time clock with 10 years battery backup without external power

  • All system parameters such as serial number are store in non-volatile memory (EEPROM) inside the micro-controller

  • 3 channels of Isolated digital input for monitoring of digital alarm

  • 16 channels of high impedance digital inputs or connection to Analog-To Digital type Shaft Encoder in Float-And-Counterweight water level sensor

  • 2 channels of volt-free digital output (240V 1A each), use external interposing relay for flood warning siren control, pump control, etc.

  • 2 channels of high-speed pulse input accept contact closure signal or 5V-13V DC voltage, user configurable for opto-isolation provide flexibility in connection and for interface to all type of sensors for event logging such as tipping bucket type rain gauge. Pulse input equipped with efficient hardware filtering to eliminate faults multiple rainfall event record due to poor tipping bucket contact (settable for no filtering, 2 pulse/second or 1 pulse/second)

  • 4 channels of high accuracy differential/ single-ended analogue inputs with Instrument Operations Amplifier (0-20mA, 4-20mA, 0-5V, 0-10V)

  • Built in watchdog circuitry, RTU never hang

  • Removable terminal block to ease maintenance work

  • Power surge protection by using Metal Oxide Varistor (MOV) and Suppression Diode on supply and digital input

  • Low power consumption, overall power consumption is less then 1m-Ampere Hour (AH) good for long terms operation without charging or battery change, able to operate more then 1 years on 24AH maintenance free battery

     Specification Highlights
 
  • MICROCONTROLLER BASE CPU
  • DUAL WATCHDOG TIMERS
  • REAL-TIME CALENDAR CLOCK WITH AT LEAST 10-YEARS DATA RETENTION
  • REAL TIME DATA AND DATA LOGGING

Technical Specification for ST23 SMS RTU
 
    Advantages
 

  • ST23 is a compact / embedded single board controller card which ease the work of trouble-shooting and maintenance

  • ST23 has direct connection to GSM MODEM of all brand (Wavecom, Siemen, etc.)

  • ST23 support latest data request through Missed Call beside SMS request (User no need to pay for the request SMS, only the reply data is chargeable)

  • ST23 support direct alarm reporting to maximum 20 users, no congestion of alarm pending to send from Master Station

  • ST23 can provide direct connection to satellite equipment (INMARSAT-C / ACESat) It can be installed anywhere in the world!

  • ST23 has its pulse capturing algorithm to give a fast and accurate pulse input, no erroneous pulses

  • ST23 has smart & accurate analogue input algorithm with Moving Average to give a stable and accurate 4-20mA output conversion

  • ST23 comes with a standard set of keypad and LCD interface for user friendly interface

  • ST23 has integrated data logging facilities which can store up to 12 months data based on 1 hour interval (based on 4 parameters with date & time stamp)

  • ST23 has flexible communication configuration include store-and-forward (SAF), RMU can act as a repeater!

  • The ST23 has very low power consumption specially designed for solar powered or battery only operation

  • The ST23 RTU is designed for harsh environment which minimise the use of connectors and plug in circuit board

  • Application software embedded in the ST23 runs under a powerful and fast real-time multitasking operating system. Modification on RTU's operation can be done in days by our local programmer


 
    Photo Gallery
 

Internal view of ST23 RTU

External view of ST23 RTU with a typical ultrasonic water level transmitter

  
 
    SMS Communication Mode
 

Short Messaging System (SMS) is picking up as one of a popular communication media for remote alarm monitoring system. It is particularly simple in implementation with a medium monthly access fees.

The communication between the SMS RTU and Central Monitoring System (CMS) is proposed to utilise GSM Network and communicate via Short Messaging System (SMS). In situation where GSM network is not available, the System proposed can be easily expanded to utilise VHF/UHF leased-frequency radio link, dial-up Public Switched Telephony Network (PSTN), Telekom 4-wire lease-line or through satellite communication (e.g. INMARSET-C, AceSat). In this system, SMS/GSM Network is proposed for linkage between the CMS and RTU due to it’s simplicity in installation and wide spread of GSM Mobile network in most part of the country.

The communication protocol proposed utilize Short Messaging System (SMS). Full SMS software driver is installed in the RTU which define how the RTU shall send SMS through the GSM MODEM to the Central Monitoring Station (CMS) and / or mobile phone.

The ST2003 support six (6) types of SMS communication modes as follows:
 

  • SMS RTU automatic report alarm to operators mobile phone

  • SMS RTU reply real-time data upon request from mobile phone

  • SMS RTU automatic report logged data to CMS

  • SMS RTU dump all logged data upon request from CMS

  • SMS RTU automatic report alarm to CMS

  • SMS RTU automatic report alarm/command to another RTU for pump control
 
 
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